Impedance regulating system



July 27, 1937. H. Ro'rHE l 2,088,439

IMPEDNCE REGULATING SYSTEM Filed May 6, 1930 Pc3/.sfama- Memer/N6 Pons/Yiwu@ Jig, .1; l n 12ga- Hons Roma BY ATTORNEY Patented July 27, 1937 IM'PEDANCE REGULATING SYSTEM Horst Rothe, Berlin, Germany, assis-nor to Telefunken Gesellschaft fr Drahtlose-Telegraphie m. b. H., Berlin, Germany, a corporation o! Germany Application May 6, 1930, serial No. 450,111

In Germany May 11, 1929 22 Claims.

'I'he present invention relates to variable impedances and more particularly to means for producing inertialess variable capacitive or inductive impedances.

For modulating, regulating and similar purposes, recourse is had frequently inradio technics to impedances the value of which are varied within certain limits'by auxiliary potentials or currents rather than mechanically. It often happens that impedances must be regulated or adjusted from a remote point by way of a line, say, for modulating or regulating a transmitter station or some other alternating current apparatus. For all of these purposes, as far as applicant l5 is aware, only iron-cored choke coils have heretofore been available, the inductance thereof being varied by varying the biasing magnetizing current of the iron-core. However, whenever very high frequencies are involved, such coils are unserviceable because of the presence of the iron core, not to mention the further disadvantages that they involve comparatively high losses, and that their time constants are high. An object of the present invention is to disclose ways andy $5 means of creating both capacities as well as inductances suited also for extremely high frequencies, and which follow changes in electrical conditions practically without inertia, such variations, ii desired, being accomplished from a remote point.

Other objects of the invention will be apparent from the following detailed specification of the invention when read in connection with the drawing, in which,

s5- Fig. 1 illustrates generally and schematically the principles involved in the invention; and,

Figs. 2 through 6 illustrate practical examples of some of the uses to which the invention may be put.

It is known that in a thermionic tube I comprising a control grid (Fig. 1) and whose plate circuit contains the apparent impedance Ra, a complex resistance Rsch is transferred between control grid and filament of the tube, when the grid and the plate are associated by a resistance Rga, the size of the latter being readily determined mathematically if desired. In accordvance with this disclosure the resistance transferred between grid and filament as a circuit element is utilized to obtain the desired variation, the variation of said quantity being insured by varying the plate resistance Ra or the internal tube resistance Ri between the anode and-n1ament,or both, this being accompushame by simple means. The variations of resistance Ra or Ri may follow modulating potentials.

Thenature of this transferred resistance and its variation shall be explained by a number of practical examples: '1

Fig. 2 illustrates the simplest circuit scheme comprising a capacity Cga between grid and plate which may be the capacitance inherent in the grid plate association, though, if necessary, the

, plate grid capacity may be increased by the aid 10 of an external supplementary capacity. In the v plate circuit there is an invariable ohmic resistance Ra to which is shunted (arranged in parallel) the natural capacity inherent in the tube between the cathode and the plate. 'Ihe variation of the Vtransferred resistance Rsch is effected by varying the grid biasing potential of the tube with the result that the working point is shifted to a point alongthe tube characteristie having either a higher or a lower internal tube resistance. The biasing potential may be applied from any source to Eg.

Fig. 3 illustrates another conceivable circuit arrangement in which between the grid and the plate of the tube I is a capacity Cga. 'Ihe plate resistance Ra in this modification consists of the cathodeto anode resistance of tube 2. Hence, it is also in this instance predominantly ohmic .in nature, and by varying the grid biasing potential Eg of the tube 2 it can be altered within wide limits. It can be easily found by calculation that the resistance transferred between grid and filament in tube l consists of a capacity and a positive ohmic resistance in shunt relation thereto, the size of both components being predicated upon Ra. The theoretical liminal values between which the capacity may be changed when varying Ra amount to respectively where D denotes the reciprocal amplification factor. What must be borne in mind in this connection is that in parallel relation to this transferred resistance there exists the inherent or natural grid reactance (ohmic resistance and capacity). A more effective change of Rsch is attainable by the simultaneous alteration of Ra and Ri in opposite senses.

On account of the inherent capacitance be- 50 tween lament and plate of every tube, the circuit schemes shown in Figs. 2 and 3 are unsuited for extremely high frequencies. Where such high frequencies are dealt with, the plate resistance (impedance) as shown in Fig. 4, must 55 consist of an oscillation circuitthe damping of which is inuenced by means of tube 2. Also for this case the resistance Rsch can be calculated as above indicated. The capacitive component then changes also inside the limits above given, while the ohmic'component must assume either positive or negative values according to whether the impedance of the oscillation circuit is ohmic, reactive or inductive.

In cases where a variable inductance is re-v quired, as shown in Fig. 5, grid and plate mustbe associated by an inductance in series as shown with a'blocking condenser to block out the plate direct current from the grid.

An inductive reactance between grid and filament is obtainable also by means of a neutralized circuit scheme as illustrated in Fig. 6. In case the condenser CN is greater than the inherent grid plate capacity Cga, the resistance transferred in this arrangement, Rsch, contains an inductive and a negative ohmic component. This phase shift of the transferred resistance is obtained by that the transferred resistance is connected with a point of the plate circuit where the potential presents a phase displacement angle of 180 degrees in vrelation to the plate potential.

I claim: 1. A device for producing an impedance which may be varied linearly in accordance with potential variations comprising, a thermionic tube having a control grid, a cathode and an anode, an impedance connected between said anode and control grid, a variable resistance connected in parallel with the internal impedance of the tube between said anode and cathode of said tube, andadeviceconnected with said variable resistance and energized by said potential variations for varying said resistance in accordance with said potential variations whereby resistance effects are produced between said control grid and cathode which are linear with respect to said potentials.

2. Means for producing an impedance which varies linearly with respect to modulation potential variations comprising, a thermionic tube having a control grid, a cathode and an anode, a reactance connected between said anode and control grid, and a variable resistance connected in parallel with the internal impedance between the anode and cathode of said tube comprising an additional thermionic tube having its anode electrode connected with the anode of said rst named tube and its input electrodes connected to a source of modulating potentials, whereby impedance effects which vary in accordance with said modulating potentials are produced between the control grid an`d cathode of said rst named tube which are linear with respect to said modulating potentials.

3. A device for producing an electrical characteristic which may be varied linearlyu in accordance with potential variations comprising, a thermionic tube having a control grid, a cathode and an anode, a capacity connected between said anode and control grid, a reactance connected in parallel with the anode to cathode impedance of said tube, and a variable resistance connected in parallel with the internal impedance between the anode and cathode of said tubecomprising an additional. tube having its anode to cathode impedance connected in parallel to said reactance and its control grid connected to a. source of potentials which vary, whereby resistance effects are produced between said control grid and cathode of said tlrst named tube which are linear with respect to said potentials which Vary.

4. A device for producing an electrical characteristic which may be varied directly in accordance with modulating potential variations comprising, athermionic-tube,having -an anode, a

cathode and a control grid, an inductance con-,

nected between said anode and said control grid, a tuned circuit connected with said anode, said tuned circuit` being in eect in parallel with the internal resistance between said anode and said cathode, an additional thermionici tube having its output electrodes connected in parallel with said tuned circuit, and means for applying modulating potentialsr to the input electrodes of said additional tube, whereby a resistance effect proportional to said modulating potentials is produced between the control grid and cathode of said first named tube.

5. A device as recited in `claim 4 in which said inductance connected between the control grid and anode of said rst named-tube is in series with a capacity.

. 6. The method of opera-ting a triode as a4 variable impedance element in a circuit including a reactive coupling between the grid and anode elements of said triode, and a resistance connected between the cathode and anode thereof, which comprises varying said resistance to produce consonant variations of the effective anode-grid reactance of said triode.

7. The method of 'operating a triode as a variable impedance element in a circuit including a reactive coupling between the grid and anode elements of said triode, and a resistance connected between the cathode and anode thereof, which comprises cyclically varying said resistance to produce consonant variations of the eiective anode-grid reactance of said triode.

8. A circuit of variable reactance comprising a vacuum tube including a. cathode, an anode, and a, grid and having reactive coupling between said anode and grid, and a second vacuum tube connected as an output resistor between the anode and cathode of said rst tube, said second tube being variable in resistance to produce consonant Variations in reactance between the cathode and grid of said rst tube.

9. A circuit of Variable reactance comprising a vacuum tube including a cathode, an anode, and a grid, a reactive element connected between said grid and anode, and a second vacuum tube connected as an output resistor between the anode and cathode of said rst tube, said second tube being variable in resistance to produce consonant variations` in reactance between the lcathode and grid of said first tube.

10. A circuit of variable reactance comprising a vacuum tube including a cathode, an anode, and a grid, a capacitance externally connected between said grid and anode, and a second vacuum tube connected as an output resistor between the anode and cathode of said first tube, said second tube being variable in resistance to produce consonant variations in reactance between the cathode and grid of said rst tube. I

1l. A circuit of variable reactance comprising a. vacuum tube including a cathode, an anode, and a grid, an inductance connected between said cathode and anode, and a second vacuum tube connected as an output resistor between the anode and cathode of` said first tube, said second tube being variable in resistance to produce consonant variations in reactance between the cathode and grid of said first tube.

12. A variable reactance circuit comprising a vacuum tube including a cathode, an anode, and a grid, and having reactive coupling between said anode and grid, a second vacuum tube connected as an output resistor between said anode and cathode, and means for cyclically varying the effective resistance of said second tube to produce corresponding variations in the effective cathode-grid reactance of said rst tube.

13. The method of employing an amplier tube having input and output circuits to -vary the impedance of said input circuit which comprises reactively connecting said input and output circuits, discarding the power developed in said output circuit, and varying said output circuit to vary the reaction thereof upon said input circuit.

14. The method of operating a tube as a Variableimpedance element in a circuit including an impedance coupling external to the tube between the grid and anode elements of said tube, and an impedance connected between the cathode and anode thereof, which comprises varying said last named impedance to produce consonant variations of the effective anode grid impedance to saidv tube.

15. A circuit of variable impedance comprisin a vacuum tube including a. cathode, an anode, and a` grid, an impedance element connected between said grid and anode, and a second vacu- -electrical characteristic of the unit for producing desired changes in the value of said capacity.

17. A variable electronic condenser unit comprising. an electron discharge tube having at least a. cathode, grid and anode, the grid circuit of the tube comprising the condenser, condensive means common to the grid and anode circuits of the tube for providing a predetermined capacity in said condenser, and means for adjusting an electrical characteristic o! the unit for producing desired changes in the value of said capacity. v i

18. An adjustable condenser unit comprising a tube having at least a cathode and two cold electrodes, the circuit between the cathode and one of the cold electrodes comprising the condenser, a. capacitance common to both of said cold electrodes for producing.a desired capacity value in the said condenser, and means for varying an electrical characteristic of the unit for changing the said value.

19. An adjustable lcondenser unit comprising a tube having at least a cathode and two cold electrodes, the circuit between the cathode and one of the cold electrodes comprising the condenser, a capacitance common to both of said cold electrodes for producing a desired capacity value in the said condenser, and means for varying an electrical characteristic of the unit, such as the amplication factor oi the tube, for changing the said value.

20. A variable condenser unit comprising a tube provided with a cathode, plate and control electrode, the circuit between the cathode and control electrode comprising the condenser, a condenser connected between the plate and control electrode to augment the capacity of said f' in the said capacity.

22. An adjustable voltage operated capacitance comprising a tube provided with a cathode and at least a grid and plate, the capacity between the grid and cathode comprising-the said capacitance, auxiliary capacitance being provided between the grid and plate to augment the value of said iirst capacitance, and means for adjusting the space current now oi the tube in a predetermined manner for producing desired variations in the value of said first capacitance.

HORST ROTI-IE. 

